JP7027195B2 - Motor system and its control method - Google Patents

Description

The present invention relates to an electric motor system and a control method thereof.

Conventionally, a supercharger that compresses the combustion air of an internal combustion engine and sends high-density air into the combustion chamber is known. For example, it is widely used in a two-stroke low-speed engine such as a marine diesel engine or a power generation diesel engine. It is used. In such a turbocharger, a compressor that compresses combustion air and a turbine that is a drive source of the compressor are connected to a rotating shaft, and are housed in a casing to rotate integrally. The turbine is driven by the energy possessed by the exhaust gas of the internal combustion engine.

As the above-mentioned turbocharger, for example, a hybrid turbocharger in which a high-speed generator motor is connected to a rotating shaft is known. This hybrid turbocharger can supply pressurized combustion air to the internal combustion engine in the same manner as a normal turbocharger, and can also generate electricity by using surplus exhaust gas energy to supply electric power.

Further, an electrically assisted supercharger in which a miniaturized motor is adopted in place of the generator motor of the hybrid supercharger described above and the motor is built in the supercharger is known. In this electrically assisted turbocharger, a miniaturized motor is attached to a shaft extension portion in which the rotation shaft is extended toward the intake air introduction path side. In this case, since the weight of the rotor of the motor can be sufficiently supported by the existing supercharger bearing, an overhang structure that does not require a bearing dedicated to the motor, that is, does not have a bearing dedicated to the motor is common. .. In such an electrically assisted turbocharger, for example, when a sufficient amount of exhaust gas cannot be obtained when the load on the main engine is low, the scavenging pressure to the main engine becomes insufficient, so the electric motor is energized instead of using the conventional auxiliary blower. , Assists the drive of the compressor by adding the driving force of the motor.

Japanese Unexamined Patent Publication No. 2015-158161

By the way, a motor using a permanent magnet for a rotor is adopted as a generator motor of a hybrid supercharger and a motor of an electrically assisted supercharger as described above. Since the rotation speed of such a motor is proportional to the counter electromotive force, for example, when designing a power conversion device (inverter, etc.) for driving the motor, the voltage corresponding to the maximum rotation speed of the motor is defined as the rated voltage. There is a need to.
Moreover, in the design of the motor, it is necessary to design the rated voltage and the rated current in a well-balanced manner from the required output power. In order to reduce the size of the motor, it is necessary to lower the rated current, but if the rated current is lowered, it is necessary to raise the rated voltage in order to obtain a constant output. Then, when the rated voltage of the motor is increased, the rated voltage of the power conversion device must be increased accordingly, and it is necessary to adopt a power conversion device having high withstand voltage performance.
In particular, in the case of an electrically assisted turbocharger that employs an overhang structure, it was necessary to mechanically design not only the motor but also the power converter to withstand the maximum rotation speed of the turbocharger. ..

The present invention has been made in view of such circumstances, and in an electric motor system connected to a rotating shaft of a supercharger, the size of the electric motor can be reduced without excessively increasing the withstand voltage performance of the power converter. It is an object of the present invention to provide a motor system that can be reduced and a control method thereof.

A first aspect of the present invention is a connection switching means for switching between a motor connected to a rotary shaft of a supercharger, a power conversion means for supplying power to the motor, and a connection / disconnection between the motor and the power conversion means. And a control means for controlling the connection switching means, the control means includes a first control means for determining whether or not the rotation speed of the electric motor is equal to or higher than the first threshold value, and a rotation speed of the electric motor. Is provided with a second control means for determining whether or not is equal to or higher than the second threshold set to a value larger than the first threshold, and the rotation speed of the motor is equal to or higher than the first threshold by the first control means. When it is determined that the number of revolutions of the motor is equal to or higher than the second threshold value by the second control means, the connection between the motor and the power conversion means is disconnected. The connection switching means is controlled, and the second threshold value is set to the maximum rotation speed determined from the allowable voltage of the power conversion means or a value having a predetermined margin for the maximum rotation speed, and the said. It is a motor system that is set to a value smaller than the maximum rotation speed of the supercharger.

According to the electric motor system according to this aspect, when it is determined that the rotation speed of the electric motor is equal to or higher than the first threshold value or the second threshold value, the connection between the electric motor and the power conversion means is disconnected, so that the rated voltage of the electric motor is used. At the same time, it is not necessary to design the withstand voltage of the power conversion means to be high. In other words, by setting the first threshold and the second threshold according to the rotation speed according to the withstand voltage performance of the power conversion means, the power conversion means and the electric motor can be used only in the rotation speed region that the power conversion means can withstand. It becomes possible to maintain the connection with. This eliminates the need to raise the withstand voltage performance of the power conversion means to a voltage corresponding to the maximum rotation speed of the turbocharger, and makes it possible to adopt a relatively inexpensive power conversion means.

For example, in a supercharger system such as an electrically assisted turbocharger, energization (assist) by the motor is not always performed up to the maximum rotation speed of the turbocharger, for example, up to about half of the rotation speed. Only needed. Therefore, by setting the first threshold value to the lower limit value of the rotation speed region in which the motor does not need to be energized, the power supply to the motor can be limited to the minimum rotation speed range, and unnecessary power can be used. It is possible to eliminate consumption. Further, according to the electric motor system according to this aspect, since the rotation speed of the electric motor and each threshold value are compared in both the first control means and the second control means, it is possible to provide redundancy in the control.

The electric motor system may include a rotation speed measuring means for measuring the rotation speed of the turbocharger, and the first control means may use the measured value of the rotation speed measuring means as the rotation speed of the electric motor.

The electric motor system includes a voltage measuring means for measuring a line voltage output from the power conversion means, and the second control means obtains the rotation speed of the electric motor by using the measured value of the voltage measuring means. May be.

The electric motor system includes a current measuring means for measuring a current flowing from the power converting means to the electric motor in a state where the electric motor and the electric power conversion means are connected, and the second control means is the current measuring means. The rotation speed of the electric motor may be obtained by using the measured value of the means.

In the electric motor system, the first control means is the rotation speed of the electric motor obtained by using the measured value of the voltage measuring means and the rotation speed of the electric motor obtained by using the measured value of the current measuring means. At least one of them may be acquired from the second control means, and it may be determined whether or not the rotation speed of each motor acquired from the second control means is equal to or higher than the first threshold value.

In this way, not only the measured value of the rotation speed measuring means, but also the rotation speed of the motor obtained from the measured value of the voltage measuring means and the rotation speed of the motor obtained from the measured value of the current measuring means are used for the determination. It is possible to give redundancy to the measured values.

In the electric motor system, the control means is set to have a rotation speed of the electric motor less than the first threshold value when the connection between the electric motor and the electric power conversion means is disconnected by the connection switching means. When it is less than three threshold values, the connection switching means may be controlled so as to connect the electric motor and the power conversion means.

According to the above configuration, it is possible to avoid connecting the power conversion means and the electric motor in the rotation speed region where the rotational speed of the electric motor exceeds the third threshold value.

In the electric motor system, the first control means determines whether or not the rotation speed of the electric motor is equal to or higher than the fourth threshold value set to a value larger than the first threshold value and smaller than the second threshold value. When the rotation speed of the electric motor is equal to or higher than the fourth threshold value, the connection switching means may be controlled so as to disconnect the connection between the electric motor and the power conversion means.

According to the above configuration, when the first control means determines that the rotation speed of the electric motor is equal to or higher than the fourth threshold value, the first control means connects the electric motor and the power conversion means to the connection switching means. Control is performed to shut off. As a result, the connection between the motor and the power conversion means can be quickly cut off. Further, even when the connection switching means cannot be controlled by the second control means due to a failure of the second control means or the like, the connection switching means can be controlled from the first control means, so that the redundancy is further enhanced. Is possible.

In the motor system, the first control means is a higher-level device of the second control means, and as the second control means, a control means having a faster processing speed than the first control means may be adopted. ..

According to the above configuration, in the second control means whose processing speed is faster than that of the first control means, the rotation speed determination process using the second threshold value higher than the first threshold value is performed. As a result, if the first control means does not detect that the rotation speed of the electric motor is equal to or higher than the first threshold value, and the second control means determines that the rotation speed of the electric motor is equal to or higher than the second threshold value. However, it is possible to quickly control the connection switching means.

The second aspect of the present invention is a supercharger system including the electric motor system according to any one of the above and a supercharger in which the electric motor included in the electric motor system is connected to a rotating shaft.

A third aspect of the present invention is a ship including the supercharger system described above and an internal combustion engine to which outside air is pumped by the supercharger system.

A fourth aspect of the present invention is a control method of an electric motor system including an electric motor connected to a rotating shaft of a supercharger and a power conversion means for supplying electric power to the electric motor, wherein the rotation speed of the electric motor is the same. A first control means for determining whether or not the motor is equal to or higher than the first threshold, and a second for determining whether or not the rotation speed of the motor is equal to or higher than the second threshold set to a value larger than the first threshold. A control means is provided individually, and when the first control means determines that the rotation speed of the motor is equal to or higher than the first threshold value, or the second control means determines that the rotation speed of the motor is the first. When it is determined that the value is 2 thresholds or more, the connection between the motor and the power conversion means is disconnected, and the second threshold is the maximum rotation speed determined from the allowable voltage of the power conversion means or the maximum rotation. This is a control method for a motor system in which the number is set to a value having a predetermined margin and is set to a value smaller than the maximum rotation speed of the supercharger.

According to the present invention, in an electric motor system connected to a rotary shaft of a turbocharger, it is possible to reduce the size of the electric motor without excessively increasing the withstand voltage performance of the power converter.

It is a figure which showed the schematic structure of the supercharger system which concerns on 1st Embodiment of this invention. It is a figure which showed an example of various sensors provided in the electric motor system which concerns on 1st Embodiment of this invention. It is a figure which showed the schematic structure of the control device which concerns on 1st Embodiment of this invention. It is a flowchart which showed the processing procedure of the overturning detection process executed by the 1st control unit during the motor synchronization of the motor system which concerns on 1st Embodiment of this invention. It is a flowchart which showed the processing procedure of the overturning detection processing executed by the 2nd control unit during the motor synchronization of the motor system which concerns on 1st Embodiment of this invention. It is a flowchart which showed the processing procedure of the motor synchronization determination processing which is executed by the 1st control unit in the motor asynchronous of the motor system which concerns on 1st Embodiment of this invention. It is a flowchart which showed the processing procedure of the overturning detection processing executed by the 1st control unit during the motor synchronization of the motor system which concerns on 2nd Embodiment of this invention.

[First Embodiment]
Hereinafter, the first embodiment of the motor system of the present invention and the control method thereof will be described with reference to the drawings. In the following embodiment, a case where the motor system of the present invention is applied to an electrically assisted turbocharger applied to a ship will be illustrated and described.

FIG. 1 is a diagram showing a schematic configuration of a turbocharger system according to a first embodiment of the present invention. As shown in FIG. 1, the supercharger system is a system mounted on a ship and used, and includes a supercharger 10 and an electric motor system 1 as a main configuration.
The turbocharger 10 includes an exhaust turbine 21 driven by exhaust gas discharged from a marine diesel engine (internal combustion engine) and a compressor 23 driven by the exhaust turbine 21 to pump outside air to the internal combustion engine. As described above, the turbocharger 10 utilizes the engine exhaust gas discharged from the marine diesel engine as the driving force of the compressor 23.

The electric motor system 1 includes an electric motor 30, a power conversion device 20, and a control device 40 as main configurations.
The electric motor 30 is connected to the rotating shafts of the exhaust turbine 21 and the compressor 23, and assists the driving of the compressor 23.
The power conversion device 20 is connected between the electric motor 30 and the inboard system (power supply) 16 and is driven based on a control signal from the control device 40 to supply three-phase AC power to the electric motor 30. The power conversion device 20 includes, for example, a converter 12, an inverter 14, and a smoothing capacitor 18 provided on a DC bus 15 connecting the converter 12 and the inverter 14 as a main configuration.

The converter 12 converts the three-phase AC power from the inboard system 16 into DC power and outputs it to the DC bus 15. The smoothing capacitor 18 reduces DC voltage fluctuations. The inverter 14 converts the DC power supplied via the DC bus 15 into three-phase AC power and outputs it to the motor 30.
The inverter 14 is composed of, for example, a circuit formed by bridging six switching elements. The configuration of the inverter 14 is not limited to this example, and other configurations may be adopted.

Further, in the motor system 1, the three-phase electric wire connecting the inverter 14 and the motor 30 is provided with a contactor (connection switching means) 50 for switching connection / disconnection between the inverter 14 and the motor 30. The mechanism for switching the connection / disconnection between the inverter 14 and the motor 30 is not limited to the contactor. That is, it is possible to appropriately adopt a mechanism capable of switching connection / disconnection between the inverter 14 and the motor 30.
The control device 40 controls the power conversion device 20 and the contactor 50 based on the measured values of various sensors described later.

FIG. 2 is a diagram showing an example of various sensors provided in the motor system 1. As shown in FIG. 2, the motor system 1 includes voltage sensors 60a and 60b for measuring the phase-to-phase voltage supplied from the inverter 14 to the motor 30, and current sensors 70a and 70b for measuring the alternating current flowing from the inverter 14 to the motor 30. It is equipped with a rotation speed sensor 80 that measures the rotation speed of the supercharger 10. Here, in addition to the rotation speed sensor 80, a rotation speed sensor for measuring the rotation speed of the electric motor 30 may be provided. Further, the motor system 1 has a voltage sensor (not shown) for measuring the DC voltage of the DC bus 15.
In the following description, when distinguishing each sensor, the reference numerals a and b are added as described above, and when each sensor is not particularly distinguished, a and b are omitted.

In this embodiment, the case where the voltage sensor 60a measures the line voltage Vuv between the U phase and the V phase and the voltage sensor 60b measures the line voltage Vvw between the V phase and the W phase is illustrated, but the measurement is performed. The combination of line voltages is not limited to these. Similarly, the case where the current sensor 70a measures the U-phase current and the current sensor 70b measures the V-phase current is illustrated, but the combination of the measured phase currents is not limited to these.
Further, in the present embodiment, the case where two voltage sensors 60 and two current sensors 70 are provided is illustrated, but the number of installed voltage sensors 60 and current sensors 70 is not limited to this, and the control device 40 is used. The number of installations can be appropriately increased or decreased according to the information required to control the electric motor 30.

The control device 40 controls the inverter 14 based on the measured values of the various sensors 60, 70, and 80, and also controls the opening and closing of the contactor 50.
FIG. 3 is a diagram showing a schematic configuration of the control device 40. As shown in FIG. 3, the control device 40 includes a first control unit 41 and a second control unit 42.
For example, the first control unit 41 and the second control unit 42 are configured as hardware-independent devices, and are configured to be capable of exchanging information with each other.

The first control unit 41 and the second control unit 42 are both composed of a microprocessor or the like, and are, for example, a CPU, a ROM (Read Only Memory) for storing a program or the like executed by the CPU, and a work at the time of executing each program. It is equipped with a RAM (Random Access Memory) that functions as an area, a communication unit for exchanging data with other devices, and the like. As an example, a series of processes for realizing various functions are stored in a storage medium such as a ROM in the form of a program, and the CPU reads this program into a RAM or the like to process and calculate information. By executing, various functions are realized. The program is installed in a ROM or other storage medium in advance, is provided in a state of being stored in a computer-readable storage medium, or is distributed via a wired or wireless communication means. Etc. may be applied. The computer-readable storage medium is a magnetic disk, a magneto-optical disk, a CD-ROM, a DVD-ROM, a semiconductor memory, or the like.

The first control unit 41 is a higher-level device of the second control unit 42, and for example, generates a rotation speed command of the electric motor 30 according to the operating state of the supercharger 10 and gives it to the second control unit 42. Further, the first control unit 41 receives the measured value from the rotation speed sensor 80 of the turbocharger 10 and controls the opening and closing of the contactor 50 based on the rotation speed ω. Here, the rotation speed sensor 80 is a sensor that directly measures the rotation speed of an overcurrent or the like from an impeller, a rotor tip, a notch of a thrust collar, or the like, and is a sensor such as a voltage sensor 60 or a current sensor 70. It is different from the one that calculates the number of rotations by calculation based on the measured value. As an example of the first control unit 41, a PLC (programmable logic controller) can be mentioned.

The second control unit 42 is a control signal for matching the rotation speed of the electric motor 30 with the rotation speed command received from the first control unit 41 based on the voltage measurement value of the voltage sensor 60 and the current measurement value of the current sensor 70. (For example, a PWM signal) is generated, and the generated control signal is given to the inverter 14. As a result, each switching element constituting the inverter is turned on and off based on the control signal, so that electric power corresponding to the rotation speed command can be supplied to the inverter 14.
Further, the second control unit 42 controls the opening and closing of the contactor 50 based on the voltage measurement values Vuv and Vvw of the voltage sensor 60 and the current measurement values Iu and Iv of the current sensor 70. Specifically, the second control unit 42 calculates the rotation speed ωv of the electric motor 30 using the voltage measurement values Vuv and Vvw, and calculates the rotation speed ωi of the electric motor 30 using the current measurement values Iu and Iv. , The opening and closing of the contactor 50 is controlled based on the rotation speeds ωv and ωi acquired by the calculation. Further, the second control unit 42 transmits the calculated rotation speeds ωv and ωi to the first control unit 41.
Since both the method of calculating the rotation speed ωv of the motor 30 from the interphase voltage and the method of calculating the rotation speed ωi of the motor 30 from the current measurement value are known techniques, detailed description thereof is omitted here. ..

Here, since the current measurement by the current sensor 70 is possible only when the supercharger 10 is boosted (motor assist) by the electric motor 30, the current measurement value is obtained when the contactor 50 is in the open state. The contactor 50 is not controlled based on the above.
An example of the second control unit 42 is a DSP (digital signal processor). The second control unit 42 is a control unit having a faster processing speed than the first control unit 41.

Next, the contactor opening / closing process executed by the control device 40 will be specifically described with reference to FIGS. 4 to 6.
First, when the contactor 50 is closed, the inverter 14 and the electric motor 30 are connected via the contactor 50, and the inverter 14 is driven (hereinafter referred to as "motor synchronization"). The over-rotation detection process executed by the first control unit 41 and the second control unit 42, respectively, will be specifically described.

FIG. 4 is a diagram showing a processing procedure of over-rotation detection processing executed by the first control unit 41 during motor synchronization. It should be noted that this over-rotation detection process is a process that is repeatedly executed at predetermined time intervals.
First, the first control unit 41 determines whether or not the rotation speed ω measured by the rotation speed sensor 80 is equal to or greater than the first threshold value ω1 (SA1). Here, the first threshold value ω1 is set to a value smaller than the second threshold value ω2 described later. The first threshold value ω1 is, for example, the upper limit rotation speed of motoring. The motoring upper limit rotation speed means, for example, a rotation speed at which motoring should not be performed at a rotation speed higher than this, and a rotation speed at which motoring should be automatically stopped at this rotation speed.
In step SA1, if the rotation speed ω is less than the first threshold value ω1 (SA1: NO), then whether or not the rotation speed ωv most recently received from the second control unit 42 is equal to or higher than the first threshold value ω1. (SA2). As a result, when the rotation speed ωv is less than the first threshold value ω1 (SA2: NO), then whether or not the rotation speed ωi most recently received from the second control unit 42 is equal to or more than the first threshold value ω1. (SA3). As a result, when it is determined that the rotation speed ωi is less than the first threshold value ω1 (SA3: NO), it is determined that the motor 30 is not in the over-rotation state, and the process is terminated.

On the other hand, when it is determined that at least one of the above rotation speeds ω, ωv, and ωi is equal to or higher than the first threshold value ω1 (YES in any of SA1, 2, and 3), the motor 30 is in the over-rotation state. Is determined, and the connection disconnection command S_open that opens the contactor 50 is transmitted to the second control unit 42 (SA4).
When the second control unit 42 receives the connection disconnection command S_open, the inverter 14 is stopped to reduce the power supply from the inverter 14 to the motor 30 to zero, and the contactor 50 is opened in this state. As a result, the connection between the motor 30 and the inverter 14 is cut off. Here, as described above, by stopping the inverter 14 and then opening the contactor 50, it is possible to avoid an arc discharge or the like that occurs when the contactor 50 is forcibly opened under a high load state. Can be done. This makes it possible to prevent damage to the inverter 14 and the contactor 50 due to the generation of arc discharge.
In the above example, steps SA1, SA2, and SA3 have been described in this order, but the order can be changed as appropriate. Further, it is determined whether or not the motor 30 is in the over-rotation state by the three determination processes of steps SA1, SA2, and SA3. However, it is sufficient if at least one of these three determination processes is performed, and the other two determination processes are performed. Can be omitted.

Next, the over-rotation detection process executed by the second control unit 42 during motor synchronization will be described. FIG. 5 is a flowchart showing a processing procedure of the over-rotation detection process executed by the second control unit 42. It should be noted that this over-rotation detection process is a process that is repeatedly executed at predetermined time intervals. Further, since the processing speed of the second control unit 42 is higher than that of the first control unit 41, the repetition frequency of the over-rotation detection processing by the second control unit 42 may be set higher than that of the first control unit 41. .. Further, the repetition frequency may be set according to the sampling interval of the voltage sensor 60 and the current sensor 70.

First, the second control unit 42 calculates the rotation speed ωv of the electric motor 30 from the latest voltage measurement values Vuv and Vvw, and determines whether or not the calculated rotation speed ωv is equal to or higher than the second threshold value ω2 (SB1). ..
Here, the second threshold value ω2 is set to the maximum rotation speed determined from the rated voltage of the inverter 14, in other words, the maximum rotation speed at which the inverter 14 can be connected to the motor 30 during motor synchronization. The region where the rotation speed of the electric motor 30 is equal to or higher than the second threshold value is positioned as the rotation speed region leading to a serious failure. Further, originally, when the rotation speed of the electric motor 30 becomes the first threshold value ω1 or more described above, the first control unit 41 determines that the motor is in the over-rotation state, so that the electric motor 30 has the first threshold value ω1 or more. It is abnormal that it is rotating at. Therefore, when it is determined that the motor 30 is equal to or higher than the second threshold value ω2, it is required to open the contactor 50 as soon as possible. The second threshold value ω2 may be set to a value having a predetermined margin for the maximum rotation speed at which the inverter 14 can be connected to the motor 30. The second threshold value is, of course, set to a value smaller than the maximum rotation speed of the turbocharger 10.

In step SB1, when the rotation speed ωv is less than the second threshold value ω2 (SB1: NO), then the rotation speed ωi of the motor 30 is calculated from the latest current measurement values Iu and Iv, and the calculated rotation speed is calculated. It is determined whether or not ωi is equal to or greater than the second threshold value ω2 (SB2). As a result, when the rotation speed ωi is less than the second threshold value ω2 (SB2: NO), it is determined that the motor 30 is not in the over-rotation state, and the process is terminated.

On the other hand, when it is determined that at least one of the rotation speeds ωv and ωi is equal to or higher than the second threshold value ω2 (SB1 or SB2: YES), it is determined that the motor 30 is in the over-rotation state, and the contactor 50 is set. It is in the open state (SB3). Specifically, the second control unit 42 sets the power supply from the inverter 14 to the electric motor 30 to zero by stopping the inverter 14, and opens the contactor 50 in this state. As a result, the connection between the motor 30 and the inverter 14 is cut off. As described above, when the rotation speed of the electric motor 30 exceeds the second threshold value ω2, the urgency is high, so that the contactor 50 may be opened when the inverter 14 is stopped.
In the above example, steps SB1 and SB2 have been described in this order, but the order can be changed as appropriate. Further, it is determined whether or not the motor 30 is in the over-rotation state by the two determination processes of steps SB1 and SB2, but it is sufficient if at least one of these two determination processes is performed, and the other determination process is omitted. It is also possible to do.

Next, regarding the motor synchronization determination process executed by the first control unit 41 when the contactor 50 is opened and the motor 30 and the inverter 14 are not connected (hereinafter referred to as “motor asynchronous”). explain. FIG. 6 is a flowchart showing a processing procedure of the motor synchronization determination process executed by the first control unit 41 during the motor asynchronous.

The first control unit 41 determines whether or not the rotation speed ω measured by the rotation speed sensor 80 is less than the third threshold value ω3 set to a value smaller than the first threshold value (SC1). Here, the third threshold value ω3 is set in a rotation speed region in which no problem occurs even if the motor 30 and the inverter 14 are connected. As a result, when the rotation speed ω is less than the third threshold value ω3 (SC1: YES), then whether or not the rotation speed ωv of the motor 30 received from the second control unit 42 is less than the third threshold value ω3. (SC2). As a result, when the rotation speed ωv is less than the third threshold value ω3 (SC2: YES), that is, when both the rotation speeds ω and ωv are less than the third threshold value ω3 (SC1, SC2: YES), the motor It is determined that the synchronization condition is satisfied (SC3), and the connection command S_close for closing the contactor 50 is transmitted to the second control unit 42 (SC4). Upon receiving the connection command S_close, the second control unit 42 closes the contactor 50, closes the inverter 14 and the electric motor 30, and then restarts the driving of the inverter 14.
On the other hand, when at least one of the rotation speeds ω and ωv is equal to or higher than the third threshold value ω3 (SC1 or SC2: NO), it is determined that the motor synchronization condition is not satisfied (SC5), and the process is terminated.

In the flowchart shown in FIG. 6, only the rotation speed condition is adopted as the motor synchronization condition, but the present invention is not limited to this example, and the motor synchronization condition is satisfied in consideration of, for example, the operating state of the turbocharger. It may be determined whether or not.
Further, in the above example, steps SC1 and SC2 have been described in this order, but the order can be changed as appropriate.

As described above, according to the electric motor system and the control method thereof according to the present embodiment, when the first control unit 41 determines that the rotation speed of the electric motor 30 is equal to or higher than the first threshold value, or the second control unit. In 42, when it is determined that the rotation speed of the motor 30 is equal to or higher than the second threshold value, the contactor 50 is opened, the motor 30 and the inverter 14 are disconnected, and the motor 30 is transferred to the inverter 14. The counter electromotive force is cut off. This eliminates the need to raise the withstand voltage performance of the inverter 14 to a voltage corresponding to the maximum rotation speed of the turbocharger 10, and makes it possible to adopt a relatively inexpensive inverter 14.

Further, according to the present embodiment, since the over-rotation detection process is executed by both the first control unit 41 and the second control unit 42, it is possible to provide redundancy in the control.
Further, according to the present embodiment, the first control unit 41 determines whether or not the rotation speed ω measured by the rotation speed sensor 80 is equal to or higher than the first threshold value. Therefore, for example, in the second control unit 42. Even if the rotation speed ωv or rotation speed ωi cannot be received due to the failure of the rotation speed calculation function, it is possible to execute the over-rotation detection process or the motor synchronization determination process based on the signal from the rotation speed sensor 80. can.

Further, for example, the current sensor 70 cannot detect the current unless the current is flowing in the inverter 14, so that the motor synchronization is in progress in order to obtain the rotation speed ωi based on the measured value by the current sensor 70. Is a condition. On the other hand, if the voltage sensor 60 is provided on the supercharger side (motor side) 10 of the contactor 50, the voltage can be detected even in asynchronous mode, in other words, even when the contactor 50 is in the open state. The voltage can be measured. Therefore, by calculating the rotation speed ωv based on the voltage sensor 60, even if the motor is asynchronous and the rotation speed cannot be measured by the rotation speed sensor 80 for some reason, the rotation speed can be determined. Based on this, it is possible to execute the motor synchronization determination process.

Further, in the first control unit 41, by using the first threshold value lower than the second threshold value, the contactor 50 can be opened before the rotation speed of the electric motor 30 reaches the second threshold value. .. This makes it possible to disconnect the inverter 14 and the motor 30 on the safer side. In particular, since the over-rotation of the inverter 14 is positioned as a serious failure, it is possible to reduce the chance of being detected as a serious failure by performing the over-rotation detection using the first threshold value lower than the second threshold value. When the first control unit 41 does not directly control the opening and closing of the contactor 50 as in the present embodiment, the first control unit 41 determines that the rotation speed of the electric motor 30 is equal to or higher than the first threshold value. After that, a time delay such as communication time occurs until the contactor 50 is actually opened. Therefore, it is advisable to set the first threshold value in consideration of the communication period between the first control unit 41 and the second control unit 42 and the like. Specifically, the first threshold value is the rotation of the electric motor 30 from the time when the first control unit 41 determines that the rotation speed of the electric motor 30 is equal to or higher than the first threshold value until the contactor 50 is actually opened. It is preferable that the number is set within a range that does not exceed the second threshold value.

Further, the second control unit 42, which has a faster processing speed than the first control unit 41, performs over-rotation detection using a second threshold value set in the vicinity of the maximum rotation speed determined from the rated voltage of the inverter 14. As a result, when it is determined that the rotation speed of the electric motor 30 is equal to or higher than the second threshold value, the contactor 50 can be quickly opened.

Further, according to the present embodiment, not only the measured values by the rotation speed sensor 80 but also the rotation speeds of the electric motor 30 are acquired by calculation from the measured values of the voltage sensor 60 and the current sensor 70, and these rotation speeds ωv, which are acquired. Since the over-rotation detection is performed using ωi, it is possible to give redundancy to the sensor as well. This makes it possible to further increase the certainty of over-rotation detection.

[Second Embodiment]
Next, the motor system and the control method thereof according to the second embodiment of the present invention will be described. In the above-mentioned first embodiment, the over-rotation of the electric motor 30 is detected based on the first threshold value ω1 and the second threshold value ω2, but in the present embodiment, these first threshold value ω1 and the second threshold value ω2 are used. In addition, the difference is that the over-rotation state of the electric motor 30 is detected based on the fourth threshold value ω4.
Hereinafter, the motor system and the control method thereof according to the present embodiment will be omitted from the description in common with the first embodiment, and the differences will be mainly described.

FIG. 7 is a diagram showing a processing procedure of over-rotation detection processing executed by the first control unit 41 of the control device 40 during motor synchronization. It should be noted that this over-rotation detection process is a process that is repeatedly executed at predetermined time intervals, and is parallel to, time-divisioned, or a series of processes with the over-rotation detection process using the first threshold value ω1 described above. May be done as.

First, the first control unit 41 determines whether or not the rotation speed ω measured by the rotation speed sensor 80 is equal to or higher than the fourth threshold value ω4 (SD1). Here, the fourth threshold value ω4 is set to a value larger than the above-mentioned first threshold value ω1 and smaller than the second threshold value ω2. As a result, when the rotation speed ω is less than the fourth threshold value ω4 (SD1: NO), then whether or not the rotation speed ωv most recently received from the second control unit 42 is the fourth threshold value ω4 or more. (SD2). As a result, when the rotation speed ωv is less than the fourth threshold value ω4 (SD2: NO), then whether or not the rotation speed ωi most recently received from the second control unit 42 is the fourth threshold value ω4 or more. (SD3). As a result, when it is determined that the rotation speed ωi is less than the fourth threshold value ω4 (SD3: NO), it is determined that the motor 30 is not in the over-rotation state, and the process is terminated.

On the other hand, when it is determined that at least one of the above rotation speeds ω, ωv, and ωi is equal to or higher than the fourth threshold value ω4 (YES in any of SD1, 2, and 3), the motor 30 is in the over-rotation state. At the same time, it is determined that a serious failure may occur, and the contactor 50 is opened (SD4). As a result, the connection between the motor 30 and the inverter 14 is cut off. In this way, when it is determined that the rotation speed of the motor is equal to or higher than the fourth threshold value ω4, the first control unit 41 outputs a signal for directly disconnecting the contactor 50 from the contactor 50. As a result, the contactor 50 can be quickly opened as compared with the case where the contactor 50 is controlled via the second control unit 42.

As described above, according to the electric motor system and the control method thereof according to the present embodiment, when the rotation speed of the electric motor 30 is determined by the first control unit 41 to be the fourth threshold value ω4 or more, the first control unit A signal for opening the contactor 50 is directly output from the contactor 50 to the contactor 50. As a result, the time until the contactor 50 is opened can be shortened as compared with the case of the over-rotation detection process based on the first threshold value described above, and the motor 30 and the inverter 14 are quickly disconnected. Can be. Further, in addition to the above-mentioned first threshold value ω1 and second threshold value ω2, the over-rotation detection process is performed using the fourth threshold value ω4 set to a value larger than the first threshold value ω1 and smaller than the second threshold value ω2. As a result, for example, even if the over-rotation detection process based on the above-mentioned second threshold value ω2 or the open control of the contactor 50 cannot be performed due to a failure of the second control unit 42 or the like, the first control unit 41 can directly perform the operation. It is possible to detect a serious failure and control the opening of the contactor 50. This makes it possible to provide redundancy and enhance safety.

Although it is difficult for the first control unit (PLC) 41 to detect the rotation speed deviating from the original rotation speed, the rotation speed that can be detected by the second control unit (DSP) 42 varies from the original rotation speed. Even if a deviated rotation speed is detected, it may be determined that the set threshold has been exceeded. Therefore, it is preferable that the second threshold value ω2 is set to a value as higher as possible than the fourth threshold value ω4. In other words, it is preferable that the difference between the fourth threshold value ω4 and the second threshold value ω2 is as large as possible. This makes it possible to avoid erroneous detection by the second control unit 42. Further, for this reason, the second threshold value ω2 is set to a relatively large value, in other words, a value at which false detection by the second control unit 42 is unlikely to occur, so that the first threshold value ω1 and the second threshold value ω2 are set. By setting the fourth threshold value ω4 between and, it becomes possible for the first control unit 41 to detect an abnormality at an early stage before the overturn detection is performed by the second control unit 42.

Although the present invention has been described above using the embodiments, the technical scope of the present invention is not limited to the scope described in the above embodiments. Various changes or improvements can be made to the above embodiments without departing from the gist of the invention, and the modified or improved embodiments are also included in the technical scope of the present invention.
For example, in the present embodiment, the case where the motor system of the present invention and the control method thereof are applied to the motor system of the electrically assisted supercharger mounted on a ship has been described as an example, but the application destination of the present invention is electric. Not limited to assist superchargers. For example, the present invention may be applied as an electric motor system of a hybrid supercharger in which an electric assist supercharger is further equipped with a power generation function.

Further, in the first embodiment, the case where the second control unit 42 controls the opening / closing of the contactor 50 has been described as an example, but the present invention is not limited to this example, and the first control unit 41 also directly opens / closes the contactor 50. The configuration may be controllable. More specifically, when it is determined that the rotation speed of the electric motor is equal to or higher than the first threshold value, the first control unit 41 may directly output an open signal to the contactor 50.

Further, in the present embodiment, over-rotation detection is performed using the rotation speed ωi of the electric motor 30 calculated based on the measured value of the current sensor 70, but the current sensor 70 is the voltage sensor 60 and the rotation speed sensor 80. Unlike the motor asynchronous state, the current cannot be measured. Therefore, the over-rotation detection process may be performed without using the rotation speed ωi of the electric motor 30 calculated from the measured value of the current sensor 70. Further, the present invention is not limited to this example, and the over-rotation detection process and the motor synchronization determination process described in the above embodiment are examples, and unnecessary steps may be deleted or new steps may be added within a range not deviating from the gist of the present invention. It is possible to add or change the processing order.

1 Motor system 10 Supercharger 14 Inverter 15 DC bus 16 Inboard system 20 Power conversion device 21 Exhaust turbine 23 Compressor 30 Motor 40 Control device 41 First control unit 42 Second control unit 50 Contactor 60 (60a, 60b) Voltage sensor 70 (70a, 70b) Current sensor 80 Rotation sensor

Claims (11)

The motor connected to the rotating shaft of the turbocharger and
A power conversion means for supplying electric power to the motor and
A connection switching means for switching connection and disconnection between the electric motor and the power conversion means, and
A control means for controlling the connection switching means is provided.
The control means is
A first control means for determining whether or not the rotation speed of the electric motor is equal to or higher than the first threshold value, and
It is provided with a second control means for determining whether or not the rotation speed of the electric motor is equal to or higher than the second threshold value set to a value larger than the first threshold value.
When the first control means determines that the rotation speed of the electric motor is equal to or higher than the first threshold value, or the second control means determines that the rotation speed of the electric motor is equal to or higher than the second threshold value. In this case, the connection switching means is controlled so as to disconnect the connection between the electric motor and the power conversion means.
The second threshold value is set to a maximum rotation speed determined from the allowable voltage of the power conversion means or a value having a predetermined margin for the maximum rotation speed, and is higher than the maximum rotation speed of the supercharger. Motor system set to a small value. A rotation speed measuring means for measuring the rotation speed of the turbocharger is provided.
The motor system according to claim 1, wherein the first control means uses the measured value of the rotation speed measuring means as the rotation speed of the motor. A voltage measuring means for measuring the line voltage output from the power conversion means is provided.
The motor system according to claim 1 or 2, wherein the second control means obtains the rotation speed of the motor by using the measured value of the voltage measuring means. A current measuring means for measuring the current flowing from the power converting means to the electric motor in a state where the electric motor and the electric power converting means are connected is provided.
The motor system according to claim 3, wherein the second control means obtains the rotation speed of the motor by using the measured value of the current measuring means. The first control means has at least one of the rotation speed of the electric motor obtained by using the measured value of the voltage measuring means and the rotation speed of the electric motor obtained by using the measured value of the current measuring means. The motor system according to claim 4, wherein the motor system is acquired from the second control means and determines whether or not the rotation speed of each motor acquired from the second control means is equal to or higher than the first threshold value. The control means is less than the third threshold value in which the rotation speed of the motor is set to be less than the first threshold value when the connection between the electric motor and the power conversion means is disconnected by the connection switching means. The electric motor system according to claim 1, wherein the connection switching means is controlled so as to connect the electric motor and the electric power conversion means. The first control means determines whether or not the rotation speed of the electric motor is equal to or higher than the fourth threshold value set to a value larger than the first threshold value and smaller than the second threshold value. The electric motor system according to claim 1, wherein the connection switching means is controlled so as to disconnect the connection between the electric motor and the power conversion means when the rotation speed of the electric motor is equal to or higher than the fourth threshold value. The first control means is a higher-level device of the second control means.
The motor system according to claim 1, wherein the second control means has a processing speed faster than that of the first control means. The motor system according to claim 1 and
A supercharger system including a supercharger in which the motor is connected to a rotating shaft. A ship comprising the supercharger system according to claim 9 and an internal combustion engine in which outside air is pumped by the supercharger system. It is a control method of an electric motor system including an electric motor connected to a rotary shaft of a turbocharger and a power conversion means for supplying electric power to the electric motor.
The first control means for determining whether or not the rotation speed of the electric motor is equal to or higher than the first threshold value, and whether or not the rotation speed of the electric motor is equal to or higher than the second threshold value set to a value larger than the first threshold value. A second control means for determining whether or not the product is provided separately.
When the first control means determines that the rotation speed of the electric motor is equal to or higher than the first threshold value, or the second control means determines that the rotation speed of the electric motor is equal to or higher than the second threshold value. In some cases, the connection between the motor and the power conversion means is disconnected,
The second threshold value is set to a maximum rotation speed determined from the allowable voltage of the power conversion means or a value having a predetermined margin for the maximum rotation speed, and is higher than the maximum rotation speed of the supercharger. How to control the motor system set to a small value.

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